In this paper, brief reviews for the synthesis of copper oxide nanoparticles by the different green routes are described. Since last few years, synthesis of nanoparticles has been attracted considerable attention. The metal oxides are important technology materials used as antibacterial, antioxidant, antifungal as well as catalysts in chemical industries and in electronic and photonic devices. Due to the applications in advanced technologies, researchers have focused more on synthesis of CuO nanoparticles with improved, cost effective ecofriendly synthetic strategies. Copper oxide nanoparticles appear as a brownish-black powder. They can be reduced to metallic copper when exposed to hydrogen or carbon monoxide under high temperature. Copper oxide nanoparticles are used in wide range of applications such as biological, catalysis, gas sensors, magnetic storage media, batteries, solar energy transformer, semiconductors, and field emission. CuO, as a P-type semiconductors exhibiting narrow band gap, have attracted great attention due to its potential application in Nano devices such as electronic, optoelectronics. …………………………………………………………………………………………………….... Introduction:-During the last few decades, the interests of scientists are increasing continuously day by day in the field of science and technology at the nanometer range. Nano-science and nanotechnology is supposed to wrap all fields of science and technology because any material particle is made up of atoms and molecules [1]. In science and technology, was considered well-progressed interdisciplinary field of research in last few year. Particularly metal oxide nanoparticles have extensive well-known their application of in many fields of science including chemical industry, electronics, biomedical sciences, biosensor, molecular catalysts, magnetic materials and drug gene delivery due to their physical and chemical properties different from those in the bulk material [2]. Main focus of nanoscience and nanotechnology is synthesis of new nanoparticles with various sizes and new morphology. Due to change in morphology strongly effects on their broadly varying properties. Much attention attracted by nanoparticles on account of their unique properties and energetic application which are strongly influenced by their size, morphology and structure. Cupric oxide nanomaterials have attracted much attention on account of their distinctive properties among other metal oxides nanomaterials [3]. Cupric oxide nanoparticles have got great consideration because it is